Role of 68Ga-PSMA PET/CT in Patients with Recurrent Prostate Cancer and its Comparison with Serum PSA Levels and Gleason Scores

Abstract: Background: Biochemical recurrence is seen in 27–53% of carcinoma prostate patients after treatment. GS (Gleason score) and baseline PSA level are a predictor of recurrence. Post- treatment persistent rising PSA levels represent the recurrence and PSMA labelled PET-CT is an important part of imaging workup in these patients. Objective: To detect the relationship between PSA levels and Gleason score in patients investigated for Gallium-PSMA-11 fused molecular imaging in biochemical recurrent carcinoma prostate. Materials and Methods: This cross-sectional study was carried out at S.I.U.T Karachi. PSMA-PET/CT scans (September 2017-January 2022) of the patient who had a biochemical recurrence and not receiving any cancer-specific treatment at least 4 weeks prior scan were included. PSA level from lab reports and GS from the histopathological reports was recorded. Biochemical recurrence were defined as when PSA level > 0.4ng/ml (post-prostatectomy) or >2.0 ng/ml higher than the nadir value after radiotherapy. PET/CT scans of 106 included patients were interpreted by the nuclear physician and radiologist team. SUVmax ≥ 2.5 was considered positive for recurrence. Local recurrences, lymphnodal, osseous, and visceral metastasis were documented. Statistical analysis was done by utilizing IBM SPSS software (version 22.0). Results: In 88 of 106 patients (83%), Gallium-PSMA-11 PET/CT scan detected at least one lesion characteristic of recurrent PCa. The median PSA level was 12.1 (.01-892.0) ng/dl. In relating PSA value, it was noted that there was a significant difference between lesion positive and negative PSMA-11 labelled Ga-68 PET/CT scan but not statically significant for GS. Local recurrences were seen in 70 patients, whereas lymph node and osseous metastases were noted in 64 and 52 scans respectively. A PSA value of 0.68 ng/ml was determined by utilizing the ROC curve with an AUC of 0.924 (95% CI 0.86-0.98) and will likely predict the positive/negative PSMA-11 Gallium PET/CT scan. Conclusion: Raised PSA level may predict the possibility of a positive Ga-PSMA-11 PET/CT scan but there was no relationship noted between GS and Ga-PSMA-11 PET/CT findings.